As the AFS proposed in order to improve the traveling safety of an automobile, there is a technique described in a Japanese patent document, JP-A-2002-160581. As shown in the schematic diagram of FIG. 1, an automobile (CAR) is provided with a steering sensor 1A for detecting a steering angle of a steering apparatus and a vehicle speed sensor 1B for detecting a vehicle speed. The detection outputs of these sensors 1A, 1B are inputted into an electronic control unit (hereinafter referred to as ECU) 2. The ECU 2 controls the irradiation area, e.g., the irradiation direction of head lamps (or headlights) 3 (swivel type lamps 3R, 3L) provided at the right and left front portions of an automobile so as to deflect in the left and right directions based on the detection outputs thus inputted thereby to change the light distribution characteristics. According to the AFS, when an automobile travels on a curved road, it is possible to deflect the irradiation direction of the swivel type lamps in accordance with the steering angle of the automobile to illuminate the portion of the road ahead of the curve, thereby being effective in improving traveling safety.
In such an AFS, when the left 3L and right 3R swivel type lamps are controlled so as to deflect merely in accordance with the steering angle, there arise various kinds of inconveniences. Various trials have been performed in order to eliminate such inconveniences. For example, Japanese patent document, JP-A-8-301005, proposes a technique in which the changing rate of the deflection of the swivel type lamps is made large so as to control the deflection angle thereof to a large extent at the time of high speed traveling, and a portion of the road farther away in the traveling direction is irradiated earlier as the speed becomes higher thereby to improve the visibility of the portion ahead of a traveling road. Further, JP-A-8-301005 proposes a technique in which, in order to eliminate a sense of incongruity due to the delay of the deflection operation of the swivel type lamps relative to a steering operation at the time of shifting from the traveling on a straight road to the traveling on a curved road, the swivel type lamps are deflected at a small changing rate even in an area where a steering angle is small like the traveling state on a straight road.
Another Japanese patent document, JP-A-62-244735, proposes a technique in which, when an automobile is steered in the left or right direction, in order to secure respective irradiation ranges in a steering direction and the direction opposite thereto to improve the visibility in a wide range, the operation timings of the deflection of left and right swivel type lamps in response to a steering angle are differentiated. In this case, for example, when an automobile is steered in the right direction, the right swivel type lamp is deflected in the right direction at first and then the left swivel type lamp is deflected in the left direction when the steering angle reaches a certain value.
As described above, in the technique disclosed in JP-A-8-301005, the deflection angle of the swivel type lamps is made large at the time of high speed traveling of an automobile to irradiate the portion ahead of a curved road. However, since both the left and right lamps perform the same deflection operation, the lamps irradiate the same area at each of the low and high speed traveling. Thus, it is difficult to achieve the irradiation which satisfies both the case where it is preferable to irradiate a large range just ahead of an automobile like at low speed traveling and the case where it is preferable to irradiate a distance area concentrically like at high speed traveling, and hence there arises a problem that the irradiation is not performed suitably in accordance with a change of the speed. Further, according to the technique of JP-A-8-301005, the changing rate of the deflection angle of the swivel type lamps with respect to the steering angle is made large at the time of traveling a road which is almost a straight road. However, since the deflection operation is not stopped completely, there arises a state where a driver feels worrisome since the deflection operation of the swivel type lamps is performed frequently as described in JP-A-8-301005.
On the other hand, in the technique disclosed in JP-A-62-244735, the operation timings of the deflection are differentiated between the left and right swivel type lamps. Thus, although it is possible to change the irradiation area, since the deflection angle with respect to the steering angle is the same at both low speed and high speed traveling, it becomes difficult to irradiate suitably a distant area ahead of an automobile traveling at a high or a middle rate of speed and to irradiate suitably the area just ahead of an automobile traveling at a low rate of speed.
Accordingly, an advantage of the invention is that it provides a vehicle lighting apparatus which can realize suitable irradiation in every traveling state of an automobile.